A multimeter is an electronic instrument widely used by electrical engineers and technicians.
This is used to measure the three basic electrical characteristics voltage, current and resistance , although it can also be used to test continuity between two point in an electrical circuit.
This device has different functionalities, since it can be used as an ammeter, voltmeter and ohmmeter .
A multimeter can be used to test electrical wiring, electric motors, batteries, and power sources.
It is one of the essential tools for any worker in the electrical area, since, in addition to being cheap, they offer a high degree of certainty when measuring the parameters already mentioned in an electrical circuit.
Although there are different types of multimeters, this article on digital ones
Table of Contents
Control of a Digital Multimeter
Screen . Easy to see and read. Most display four digits, the first of which is always zero or one. You can also always see a +/- call sign.
Main connections . A multimeter typically has up to four types of connections. Two are those that are generally used at the same time: – Common: for all types of measurements with the black (negative) and red cables.
– Volts, ohms and frequency: this connection is used to measure voltage with the red (positive) and the black wire.
– Amps and milliamps: for current measurements with the red and black leads.
– High current: this connection is usually separated. Care must be taken when using it, especially when very high current is expected.
Selector . Rotary knob to select measurement type and range.
Buttons . Used to activate other functions of the device.
Probes . These are flexible, insulated, and connect to the multimeter. They serve as the conductor of the object under test.
The basic operation and functions of a multimeter are similar in both digital and analog.
After connecting the black wire to the common port, and the red wire to any of the others, depending on what you want to measure, the knob is turned to select the appropriate function and range. For example, when this is at “20 V DC”, the device will detect direct current voltage up to 20 V. To get lower voltage readings, it will be necessary to select the mV range.
To obtain the measurement, the test leads must touch the terminal or wire to be tested. Thus, the voltage will appear on the screen. Multimeters are safe for use on energized circuits, as long as the current does not exceed the maximum capacity of the device. Similarly, the test leads should never be touched when in operation, as this could result in electrical injury .
The selector should be in the “ohm” position.
The black wire connects to the common connection.
The red wire connects to the port where the “ohm” symbol is.
Select the desired resistance value.
Measure the resistance of some element.
Measuring the voltage
The red wire connects to the port where the “V” symbol is.
The test leads are plugged into an outlet.
The test leads are removed and the range is selected lower with the selector, but higher than the voltage shown in the reading.
Tips are reinserted to obtain an accurate measurement.
The selector must be in the highest alternating current range.
The black wire connects to the common port.
Measuring the current
This procedure is a bit more complicated. The voltage and resistance are measured by putting the multimeter in parallel, but it must be in series to be able to measure intensity.
For this reason, it is necessary to open the circuit to place the red test lead there. Of course, the device must be selecting AC or DC amps to take this reading.
The voltage must be measured before.
Current clamps can also be helpful in measuring current, since with these it is not necessary to disconnect cables from the circuit.
What is a multimeter for?
Test outlets . If when inserting the test leads, the multimeter shows no voltage, then there is a problem with the circuit. It is also possible to identify a tap failure if the reading is triggered by moving the tips.
Test batteries . Extremely useful in determining which old batteries are still working.
Test switches . To perform this test, it is necessary to do it as with the resistance test. First, you have to turn off the circuit and disconnect the switch. Next, the knob should be positioned to measure resistance. Finally, the test leads should touch the switch terminals. When open, the resistance of the switch should be close to zero. If it’s too high, then it’s time to flip the switch.
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